Hudson River Park is flat and has better air quality compared to running in Midtown or Central Park. There is some distance between the highway (West Street) and the running path which I think makes the air cleaner when compared to running along the FDR on the east side. It's also a great way to view buildings that are by West Street - 101 Warren, 200 Chambers, Truffles (what does "Repent, Rent, Repeat" mean?), Meier, Superior Ink.
In Battery Park, the view is amazing and the parks aplenty. Battery Park then turns into Tribeca and the wooden path (pictured) is a welcome cushion. I always think about the grass planted here and on the High Line. These wild grass are weeds, known as lalang, in Malaysia but are decorative park grass in Manhattan.
The turn around point for a quick 34 minute run is the bathroom that is half a block north of the Superior Ink building. Passing the Richard Meier glass buildings on Perry Street is a sign Superior Ink is coming up. There is a long pier around Charles Street which attracts a fair number of sunbathers from the West Village. On the trip back, running to the edge of this pier is about another 3 city blocks.
On a longer run, after Chelsea Piers, there is another stretch of spacious, grassy, park area. I don't know the name of it, only run by it all the time. This is another local secret spot. After that, the running path turns into touristy 42 St. actually, it's first undeveloped (34 St) before it becomes touristy (42 St). That's when runners see the The Intrepid museum, cruise ships, tourists and sometimes, demonstrations as the China consulate is on W 42 St.
Up to around W 55 St, there are several piers. The reason I know the point of W 55 St is that during the past Fleet Week, I ran by the area to see where the Fleet Week ships were located. Turns out there were thousands of tourists and we decided to just do sailing from Battery Park instead.
Starting W 60 St it becomes park-like again. The Riverside Boulevard residential buildings, beginning with the Aldyn, comes into view and another turning point is the pier by W 72 St. Riverside Blvd is perhaps the second most park-oriented neighborhood after Battery Park City. Not counting Central Park because CP is not a neighborhood. The base of the pier by W 72 St has a cafe and during the summer, there are bands playing etc. By now it would be about 6 miles (one way).
There's a marina around W 80 St and during the last run, I saw this very tall ship which was about 200 feet long. There's another cafe around there. The longest I've run so far is to W 96 St by which point it's 7 miles from the starting point. Round trip would make it 14 miles.
Hudson River Park is a nice run because the air is better and because most of the park is well landscaped. For me, there is no need to brave Midtown traffic to get there unlike the Central Park runs.
By the way, my favorite shoes are the Newtons, based on a midfoot / forefoot strike style. These are more cushioned and faster than running with Vibram Five Fingers. Very natural, light and injury free. This is how running is supposed to be.